Study cholesterol gallstone recurrence and prophylaxis in patients previously treated with chenodeoxycholic acid (CDC) in the National Cooperative Gallstone Study and in whom the gallstones have dissolved completely. The Phase II Study was designed to evaluate the safety and efficacy of chenodeoxycholic acid in dissolving gallstones. This study suggested that the next steps in a complete evaluation of the drug would be to: evaluate the process of biliary lipid change and gallstone recurrence after cessation of CDC therapy; and evaluate whether low doses of CDC could be given prophylactically to prevent gallstones from reforming in patients in whom stones had been dissolved.